For many years multiple-flash stroboscopic photography has been used to show in a single picture the complete motion path of an object. This technique has been found to be a useful and instructive way of visualizing the subtle changes associated with athletic activities, for example. The apparatus for producing such photographs include a stroboscopic light source for intermittently illuminating the object in motion and a black scene background so as not to overload the photographic system which successive exposures to light. Since this technique requires development of the exposed film, the photographic approach does not provide immediate nor real-time access to the picture information.
Attempts to reproduce similar effects in television have been restricted to non-real time mixing of successive images from a recording system. Although such previous attempts produce results suitable for certain artistically satisfying and useful effects, the apparatus is expensive and the process laborious and time-consuming.
The primary object of the present invention is to provide a television display which portrays the motion of an object in a scene during a specific time interval such that in addition to its present position being shown, a plurality of earlier positions, commencing with the start of the time interval, are also depicted. Another object of the invention is to provide a system as described in the previous sentence having the capability of retaining, after termination of the specific time interval, the signal information representing the plurality of displayed object positions. Another object of the invention is to provide a display as described above in color which places no restrictions on the nature of the picture background other than what would constitute good color television practice, nor on the origination of the source of the input video signal.